Our current understanding of the global changes that occur during infection is primarily based upon transcriptional profiles of either the host or the bacteria. However, a significant component of disease progression is dependent upon posttranscriptional processes. Recent advances in the application of two-dimensional tandem mass spectrometry have dramatically increased sensitivity to allow simultaneous analyses of multiple molecules from very small biological samples. In this study, we report the comprehensive proteomic and metabolomic profiling of middle ear tissues using samples that are smaller than those typically obtained from a human biopsy. Proteomic and metabolomic analyses of samples as small as biopsies will revolutionize the elucidation of the mechanisms of pathogenesis in experimental models of disease as well as in human samples.
Otitis media (OM) is a significant disease of the pediatric population. The direct and indirect costs for the diagnosis and treatment of acute OM (AOM) in 2009 approached $3 billion and the number of all OM cases has estimated costs of treatment of up to $6 billion in the US annually. The scope of the problem is apparent with the observation that globally there are 709 million cases of AOM estimated per year of which 51% occur in children under the age of five. Monasta et al. (2012) PLoS One 7: e36226. Moreover, children attending daycare outside the home, approximated at 4 million children in the US in 2011, are 4-fold more likely to have an incidence of AOM. As a result, OM is the most common reason for a doctor's visit in school age children and is associated with significant morbidity. Long-term hearing loss is a direct consequence of untreated OM with effusion (OME). Clinical management of OM has relied heavily on antibiotic therapies (Auinger et al., (2003) Pediatrics 112: 514-520; Bauchner H, Philipp B (1998) Pediatrics 102: 142-145), which has contributed to the emergence of antibiotic resistant strains of bacteria. Novel solutions are needed for this highly prevalent disease and require extensive description of the molecular mechanisms of disease to define novel therapeutic targets.
Nontypeable Haemophilus influenzae (NTHI) predominates in approximately 50% of cases of AOM and has a significant role in OME. Holder et al. (2012) BMC Pediatr 12: 87. To better understand and ultimately prevent disease, it is imperative that we define the bacteria-host interaction during active disease. A chinchilla model of human OM has long been utilized to investigate the role of NTHI in OM. This animal model of disease has been successfully used to develop candidate vaccines aimed to prevent NTHI-mediated OM. Novotny et al., (2013) Vaccine 31: 3417-3426. In addition, mutational studies have identified NTHI gene products essential in bacterial pathogenesis. Harrison A, Santana E A, Szelestey B R, Newsom D E, White P, et al. (2013) Infect Immun 81: 1221-1233; Raffel et al., (2013) Infect Immun 81: 43-54. A limited number of transcriptional studies have assessed NTHI gene expression during OM. Whitby et al., (2013) BMC Genomics 14: 925; Mason et al., (2003) Infect Immun 71: 3454-3462. However, global analyses of the chinchilla model of OM have been limited, primarily due to the small amount of host material that can be retrieved from an animal and, until now, the absence of a chinchilla genome sequence. We have thus developed and successfully implemented analyses that assess global changes in proteins and metabolites in the chinchilla model of AOM. Using quantitative approaches, we identified a group of 105 proteins and 66 metabolites as potential targets in the development of rationally designed antimicrobial therapies. Moreover, these data represent the first global study of the host response during disease progression in vivo with techniques readily translatable to many diseases.